Various types of imaging devices form color images by combining color separation layers. For example, a photocopier or a printer may reproduce a given two-dimensional color image by combining on one sheet of paper a cyan layer, a magenta layer, a yellow layer, and a black layer. An edge in an image may be formed when there is a transition in a given color separation from a given intensity value in one region in the image (at one side of the edge) to a non-color value (white) (at the other side of the edge). When the transition of the composite image (i.e., with all separations combined) is from a color at one side of the edge to white at the other side of the edge, the edge may be referred to (e.g., in embodiments herein) as a normal edge. When the transition goes, for one separation, in one direction from a color value to white and, for another separation, in the same direction from white to a color value, the edge may be referred to (e.g., in embodiments herein) as an opposing edge.
When an edge common to a few separations is not precisely aligned, i.e., the edge at one separation does not register precisely with the same edge at the other separation, mis-registration artifacts are introduced. Trapping reduces or softens the visual impact of these mis-registration artifacts, by, for example, introducing an intermediate trap color between two abutting colors.
There is a need for improved trapping techniques that adequately reduce the mis-registration artifacts in opposing edges.